The idea of teaming up the abrasion resistance of diamond grit with the flexibility of a wire rope to make a flexible sawing rope dates back from the fifties of the previous century. Some groundbreaking patents were—without pretending to be complete—GB 759 505, U.S. Pat. No. 2,679,839, U.S. Pat. No. 2,773,495. The technology settled around the basic design wherein a multifilament wire rope is threaded with ‘beads’ wherein diamond grit is impregnated. The beads are spaced apart by means of spacers that can be steel springs or polymer sleeves or a combination of both. From the 1970's onward, the diamond sawing rope replaced the loose abrasive sawing wire wherein steel wires or strands of various shape and make entrained slurry of water with an abrasive therein. Such technology was in use for block extraction in quarries. Although the diamond wire ropes still needed a coolant, the cumbersome supply of abrasive (such as sand or steel shot) was eliminated and a much higher sawing speed and use-time for the rope was achieved.
Sawing ropes have found different uses:                They can be used on stationary machines to saw large blocks of natural stones into slabs for use in the building industry. While initially the machines were equipped with a single rope for sawing, nowadays multi wire saws are on the rise where in one single pass a whole block is sawn into slabs by multiple sawing ropes running parallel on grooved sheaves. Wire saws with as much as 52 wires are on the market.        They can be used on mobile sawing machines to extract blocks of natural stone out of a quarry. One single rope led through a vertical and horizontal bore hole is closed into a loop, tensioned by a sawing machine that progresses on tracks. The rope is shortened regularly as the block is cut through.        Various other heavy duty industrial uses such                    as the sawing of steel bar reinforced concrete pillars, and            segmenting sunken ships to remove the wreck in pieces, or            the cutting of the pillars on which off-shore oil drilling rigs are mounted when they are to be removed at the end of their life cycle                        are all successfully performed with sawing ropes.        
A variety of designs of sawing ropes has emerged specifically adapted to the various uses. Sawing ropes wherein the beads are separated by helix springs (as first described in U.S. Pat. No. 2,679,839) are still widely used to cut softer stones like limestone and marble. The beads glide over the wire rope but at regular intervals a bead is fixed to the rope or replaced by a crimped metal sleeve in order to prevent an accumulation of compressed springs when one of the beads would get snagged. Such an accumulation of energy would make the beads deadly bullets in case the wire rope would snap.
Harder stones like granite require sawing ropes having plastic separators with or without encapsulated springs. Hence the beads are better fixed to the wire rope. The separators plastically deform in case one of the beads is caught in the cut. The energy is absorbed in the plastic deformation, but all following beads accumulate in a phenomenon known as “wire collapse”. For the hardest materials like ceramics and reinforced concrete, the beads are separated by an elastomer such as rubber. A good description can be found in U.S. Pat. No. 4,907,564. The excellent adhesion between the rubber and the wire rope effectively transfers the forces on the bead to the wire rope while absorbing shocks. The adhesion is optimal when a brass coated steel wire rope is used in combination with an adhesive rubber, a combination that is very well known in tyre manufacturing.
The beads consist of a metal sleeve surrounded by an abrasive outer layer. The outer layer can be deposited electrolytically directly on the metallic sleeve as e.g. described in WO 02/40207, or it can be sintered into a ring shape and subsequently brazed or swaged to the metal sleeve as known form U.S. Pat. No. 3,847,569. The layer contains the abrasive grit—that is normally diamond—embedded in a metal or metal alloy. In case of electrolytic deposition this is usually nickel or a nickel alloy. In case of sintered rings it can comprise cobalt, copper, bronze, iron, tungsten, tungsten carbide (see e.g. EP 0486238). The layer can also be brazed directly (without sintering) on the sleeve as described e.g. in U.S. Pat. No. 7,089,925 B1.
The current size of the inner wire rope is standardised to 3.5 and 5 mm. The beads have an outer diameters of 7 to 11 mm. Hence at least 7 to 11 mm is lost in the cut. There is therefore a trend towards going to finer diameter sawing ropes that decrease the size of the cut. Such a reduced cut size is beneficial in terms of throughput as a thinner cut allows to obtain more slabs out of a single block in the same time. Normally there are from 25 to 40 beads per meter that are spaced regularly along the sawing rope. Soft stones require fewer beads per unit length than hard stones.
The way in which the sawing ropes are produced is always the same:                the beads are produced,        a wire rope is selected as the carrier,        the beads are threaded on the rope with or without springs in between,        
a thermoplastic polymer or elastomer is injection molded between the beads by placing the rope and beads in suitable mold
Possibly the beads are dressed prior to use in order to make them cut well from the start. The method to make the sawing rope is labour-intensive and slow as the mold only can contain a limited number of beads and hence the cable must be coated stepwise. Although the process can be automated, challenges remain in the productivity for making sawing ropes when going to finer diameters.
Other ways of making the sawing ropes have been suggested:                U.S. Pat. No. 4,015,931 proposes to braze sintered abrasive elements directly to a compacted wire rope. Such a brazing will affect the tensile strength of the wire rope. Alternatively, a closing ring with abrasive elements brazed thereon can be locked directly around the wire rope. Such a connection is much too weak to hold the ring in place on a steel wire rope.        WO 95/00275 and DE 2254328 suggest to insert abrasive elements during the braiding or cabling of the wire rope. Such an approach would lead to a non-uniform stiffness along the rope and a premature failure of the wires in the vicinity of the abrasive elements.        JP2006102905 and U.S. Pat. No. 6,526,960 describe a sawing rope with a polymer jacket onto which one (or more) continuous wire is helicoidally wound. The wire comprises abrasive particles.        WO 02/055248 does not describe a sawing wire rope as envisaged in this application: it describes a cutting rope that is appropriate to cut deep-frozen foodstuff or clay bricks. The cutting pieces are crimped onto a wire rope but do not comprise an abrasive, nor is the wire rope coated with a polymer.        